Mercury limit switch



July 15, 1958 J, KALAFsKY 2,843,705

MERCURY LIMIT SWITCH Filed March 1, 1955 INVENTOR. 10551 M. KALAFJ/C Y ATTOENEXS- United States Patent MERCURY LIMIT SWITCH Joseph M. Kalafsky, Cleveland, Ohio Application March 1, 1955, Serial No. 491,410

6 Claims. (Cl. 200-145) The present invention relates generally to a mercury limit switch.

It is one primary object of this invention to provide a mercury switch characterized in that an electric circuit is established in one position of the switch through a body of mercury and external switch contacts, and in that such electric circuit is broken first by interrupting the flow of electric current through the mercury, and then separating the external switch contacts to avoid sparking of the latter.

It is another object of this invention to provide a mercury switch in which the above sequence of interrupting the electric circuit through the switch is effected by the snapping or flicking of a mercury-containing capsule to utilize centrifugal force in the parting of the mercury so as to disrupt the current flow through the capsule.

Still another object of this invention is to provide a mercury switch which operates in any position so that it may be installed without regard to the position thereof.

Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawing:

Fig. 1 is a front elevation view of one embodiment of the present invention;

Fig. 2 is a diametrical cross-section view taken substantially along the line 2--2, Fig. 1;

Fig. 3 is a transverse cross-section view taken substantially along the line 33, Fig. 2;

Fig. 4 is a similar transverse cross-sectionview taken substantially along the line 4-4, Fig. 2;

Fig. 5 is a fragmentary radial cross-section view taken substantially along the line 55, Fig. 3;

Figs. 6, 7, and 8 are diagrammatic views illustrating the operability of the present invention in any desired position; and

Fig. 9 is a transverse cross-section view, similar to Fig. 3, except illustrating a modification.

Referring now more particularly to the present invention, and first to the form thereof illustrated in Figs. 1 to 5, the switch is here shown as comprising a casing 1 "and cover plate 2 secured together as by means of screws 3 and defining therein a chamber 4 containing the switch mechanism.

Extending into said chamber 4 through the central opening of the cover plate 2 is a stem 5 having a switch handle 6 non-rotatably connected thereto for rotation between the on position and the off position as indi- Patented July 15, 1958 cated by the handle pointer and the indicia on the cover plate, and the limits of such rotation may be determined as by stop pins 7 or equivalent means.

Rotatably mounted on the inner end of said stem 5 is a mercury capsule mount including a base part 8 which is formed with diametrically opposed radially projecting lugs 9 and 10 adapted to alternately engage in the notches of the spring-actuated latches 11 and 12 which are pivotally or otherwise mounted for radial inward movement to lock said base part 8 in one rotary position or the other with one lug 9 engaged with the latch 11 or the other lug 10 engaged with the other latch 12. Secured to said base part 8 is a clip part 14 adapted to securely hold a mercury capsule 15 in centered position with respect to the axis of rotation of the stem 5.

Said capsule 15 may be of familiar form and preferably includes coaxial electrodes 16 and 17 which extend toward each other from the opposite ends of the capsule a distance or about one-third the length of the capsule. The capsule 15 is filled approximately threefourths full with mercury, and the remaining space is evacuated as is customary in the art.

One electrode 16 has secured thereto at the end of the capsule a flexible electrical conductor 18 which extends to the exterior of the casing 1 as through a suitable grommet 19 or the like. The other end of the capsule 15 is provided with an external metal switch contact element 20 to which the other electrode 17 is connected, and said switch contact 20 makes electric contact with a circumferentially extending spring contact 21 mounted in the casing l and to which another lead 23 is connected.

Said stem 5 has non-'rotatably secured thereto a latch trip arm 25 which is located midway between the lugs 9 and 10 of the capsule mount base 8. As evident, the rounded outer end of said latch trip arm 25 constitutes a yieldable detent to hold the switch handle 6 in the position to which it has been rotated, and is further operative upon rotation of the stem, for instance clockwise as viewed in Fig. 3, to trip the other latch 12 to release the latter from the lug 10 engaged therein.

In so rotating the latch trip arm 25 and stem 5 as aforesaid, energy is stored in the spring 26 which is secured at its ends to the stem 5 and to the base part 8 respectively. Thus, as the switch arm 25 is rotated in a clockwise direction as viewed in Fig. 4, the cam end thereof will first move the latch 11 outwardly, and then, just when the cam end engages the other latch 12 to disengage it from the lug 18, suflicient energy has been stored in the spring 26 to cause the entire capsule and mount assembly to quickly flick or snap in the same direction, that is, clockwise as viewed in Figs. 3 and 4, to the dotted line position wherein the other lug 9 engages the latch 11 to arrest rotation.

This flicking or snapping action is so rapid that, by the time that the metal contact 20 just leaves the spring contact 21, the pool of mercury in the capsule 15 has, by centrifugal force, been separated into two parts to interrupt the current flow from one electrode 16 to the other electrode 17. Therefore, when the metal contact 20 does disengage from the spring contact 21, there will be no sparking thereat, since the electric circuit has already been broken in the mercury capsule 15.

After the rotary motion of the capsule-mount assembly has stopped, the separated mercury bodies will flow together to establish an electric circuit between the electrodes 16 and 17, but at this time the metal contacts 20 and 21 have'been separated so that current flow is not re-established. With the switch thus actuated, the cam end of the latch trip arm 25 is now engaged in the other the switch handle 6 and stem 5 in the off position.

Then, when the switch handle 6 is swung in the op" posite direction, it will, after having been swung 90, cause the latch 11 to be tripped to release the capsule and mount assembly for counterclockwise rotation back to the Figs. 3 and 4 solid line position, and in so flicking in this opposite direction again the mercury pool will be separated by centrifugalforce into two parts, whereby the metal contacts 20 and 21 come together without any current flow, and thus sparking again is avoided on the make as well as on the break.

It is to be noted that one characterizing feature of the present invention is that, by reason of the electrodes 16 and 17 extending toward each other for a distance of about one-third the length of the capsule 15 from the opposite ends of the latter. By reason of the capsu e being about three-fourths full of mercury, the switch operates exactly as described regardless of the position of the aXis of rotation. This is shown in Figs. 6, 7, and 8; and, as evident therefrom, in the rest position, the level of the pool of mercury in any position is such that an electric circuit is established between the electrodes 16 and 17, whereas when the quick flicking or snapping action occurs, the mercury pool will be separated into two parts as designated by the dotted lines in said Figs. 6, 7,and 8 to thus interrupt the current flow.

In Fig. 9, there is shown a modification of the present invention which, instead of employing relatively sliding contacts as in Fig. 3, the movable contact 3 is flicked from on position to o position by inertia, that is, by the quick deceleration or stopping of the flicking movement of the capsule-mount assembly. In this case, the electrode 17 is electrically connected to a pivotally mounted arm 36 which is preferably weighted at its outer end and which cooperates with spring detents 31 and 32 operative to hold said arm either in the solid line position wherein current flow may occur from through lead 34, detent 31, switch arm 30, electrode 17, the mercury body, the other electrode 16, and the other lead 18.

Now, when this Fig. 9 assembly is flicked as described in connection with Figs. 1 to 5, the mercury pool will again be separated by centrifugal force into two parts. Then, when the rotation of the capsule and mount assembly is suddenly stopped, the pivoted switch arm 30 swings from one position to the other, for example from the solid line position to the dotted line position, and this swinging occurs while the mercury pool is yet in parted condition so that the contacts 3%? and 31 are separated from each other without current flow therethrough.

Likewise, when the capsule and mount assembly is rotated in the opposite direction, the sudden arresting of the rotation while the mercury pool is yet separated into two parts will cause the switch arm 36) to snap by inertia from the dotted line position to the full line position, and again an electric circuit will be established without sparking at the external metal contacts. After the switch contact 30 has thus swung, the separated mercury bodies will join to complete the electric circuit through the switch.

It is to be understood that the foregoing embodiments of my invention are merely typical examples of many obvious ways of securing the desired results through the separating eifect of centrifugal force on a mercury body followed by the making and breaking of metallic external switch contacts.

In the form of the invention illustrated in Fig. 9, the capsule is preferably six times longer than the diameter thereof so that, when the mercury separation occurs, there will be a longer time interval before the separated mercury bodies rejoin each other.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims, or the equivalent of such, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In a mercury switch, the combination of a capsule partly filled with mercury and having electrodes bridged by the mercury in every position of said capsule, means supporting said capsule for rapid rotary flicking motion about an axis effective to part the mercury between the electrodes, external switch contacts in circuit with said capsule adapted to break as a consequence of capsule motion and while the mercury is thus parted, and flicking means for thus flicking said capsule, said flicking means comprising a latch engaged with said means supporting said capsule, a movable switch handle provided with a latch trip arm that first moves toward said latch and then disengages said latch at the terminal portion of rent of said handle and latch trip arm, and a spring connection between said handle and said means supporting said capsule in which energy is stored for flicking as said latch trip arm thus initially moves toward said latch.

2. In a mercury switch the combination of a tubular capsule partly filled with mercury and having a pair of electrodes which extend inwardly toward each other from the opposite ends of said capsule to spaced-apart inner termini bridged by the mercury in every position of said capsule, a pair of external switch contacts in series with the mercury-electrode circuit, and means for successively opening the mercury-eiectrode circuit and the external switch contact circuit whereby sparking of the atter is eliminated.

3. In a mercury switch, the combination of a tubular capsule partly filled with mercury and having a pair of electrodes which extend inwardly toward each other from the opposite ends of said capsule to spaced-apart inner termini bridged by the mercury in every position of said capsule, a pair of external switch contacts in series with the mercury-electrode circuit, means supporting said capsule for rotation about an axis extending transversely between the inner termini of the electrodes, flicking means operative to rapidly rotate said capsule about such axis to part the mercury between uch electrode termini by centrifugal force, and means responsive to such flicking of the capsule to open the external switch contact circuit while the mercury is thus parted in said capsule, said flicking means comprising a latch engaged with said means supporting said capsule, a movable switch handle provided with a latch trip arm that first moves toward said latch and then disengages said latch at the terminal portion of the movement of said handle and latch trip arm, and a spring connection between said handle and said means supporting said capsule in which energy is stored for flicking as said latch trip arm thus initially moves toward said latch.

4. In a mercury switch, the combination of a tubular capsule partly filled with mercury and having a pair of electrodes which extend inwardly toward each other from the opposite ends of said capsule to spaced-apart inner termini bridged by the mercury in every position of said capsure, a pair of external switch contacts in series with the mercury-electrode circuit, means supporting said capsule for rotation about an axis extending transversely between the inner termini of the electrodes, flicking means operative to rapidly rotate said capsule about such axis to part the mercury between such electrode termini by centrifugal force, and means responsive to such flicking of the capsule to to open the external switch contact circuit while the mercury is thus parted in said capsule, one of said external switch contacts being carried by said capsule and electrically connected to the outer end of one electrode for engagement and disengagement from the other external switch contact, said flicking means comprising a latch engaged with said means supporting said capsule, a movable switch handle provided with a latch trip arm that first moves toward said latch and then disengages said latch at the terminal portion of the move- F g, ment of said handle and latch trip arm, and a spring connection between said handle and said means support-' ing said capsule in which energy is stored for flicking as said latch trip arm thus initially moves toward said latch.

5. In a mercury switch, the combination of a tubular capsule partly filled with mercury and having a pair of electrodes which extend inwardly toward each other from the opposite ends of said capsule to spaced-apart inner termini bridged by the mercury in every position of said capsule, a pair of external switch contacts in series With the mercury-electrode circuit, means supporting said capsule for rotation about an axis extending transversely between the inner termini of the electrodes, flicking means operative to rapidly rotate said capsule about such axis to part the mercury between such electrode termini by centrifugal force, and means responsive to such flicking of the capsule to open the external switch contact circuit while the mercury i thus parted in'said capsule, one of said external switch contacts being mounted at the outer end of one electrode for sliding engagement relative to the other external switch contact during that portion of the rotary motion of said capsule when the mercury is parted and for disengagement from said other external switch contact while the mercury is yet parted, said flicking means comprising a latch engaged with said means supporting said capsule, a movable switch handle provided with a latch trip arm that first moves toward said latch and then disengages said latch at the terminal portion of the movement of said handle and latch trip arm, and a spring connection between said handle and said means supporting said capsule in which energy is stored for flicking as said latch trip arm thus initially moves toward said latch.

6. In a mercury switch, the combination of a tubular 6 capsule partly filled with mercury and having a pair of electrodes which extend inwardly toward each other from the opposite ends of said capsule to spaced-apart inner termini bridged by the mercury in every position of said capsule, a pair of external switch contacts in series with the mercury-electrode circuit, means supporting said capsule for rotation about an axis extending transversely between the inner termini of the electrodes, flicking means operative to rapidly rotate said capsule about such axis to part the mercury between such electrode termini by centrifugal force, and means responsive to such flicking of the capsule to open the external switch contact circuit while the mercury is thus parted in said capsule, one of said external switch contacts being carried by said capsule for inertialswinging movement out of engagement with the other external switch contact while the mercury is yet parted due to the rapid rotary flicking of said capsule, said flicking means comprising a latch engaged with said means supporting said capsule, a movable switch handle provided With a latch trip arm that first moves toward said latch and then disengages said latch at the terminal portion of the movement of said handle and latch trip arm, and a spring connection between said handle and said means supporting said capsule in which energy is stored for flicking as said latch trip arm thus initially moves toward said latch.

References Cited in the file of this patent UNITED STATES PATENTS 445,752 Hoffman Feb. 3, 1891 889,566 Wohlauer June 2, 1908 1,749,283 Hart Mar. 4, 1930 2,023,219 De Reamer Dec. 3, 1935 

